/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Objects;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.CompatibleWith;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
import org.checkerframework.checker.nullness.qual.Nullable;

A collection that associates an ordered pair of keys, called a row key and a column key, with a
single value. A table may be sparse, with only a small fraction of row key / column key pairs
possessing a corresponding value.
The mappings corresponding to a given row key may be viewed as a Map whose keys are the columns. The reverse is also available, associating a column with a row key / value map. Note that, in some implementations, data access by column key may have fewer supported operations or worse performance than data access by row key. 
The methods returning collections or maps always return views of the underlying table.
Updating the table can change the contents of those collections, and updating the collections
will change the table.
All methods that modify the table are optional, and the views returned by the table may or may not be modifiable. When modification isn't supported, those methods will throw an UnsupportedOperationException. 
See the Guava User Guide article on  Table.
Author:
Jared Levy
Type parameters:
<R> – the type of the table row keys
<C> – the type of the table column keys
<V> – the type of the mapped values
Since:
7.0/**
 * A collection that associates an ordered pair of keys, called a row key and a column key, with a
 * single value. A table may be sparse, with only a small fraction of row key / column key pairs
 * possessing a corresponding value.
 *
 * <p>The mappings corresponding to a given row key may be viewed as a {@link Map} whose keys are
 * the columns. The reverse is also available, associating a column with a row key / value map. Note
 * that, in some implementations, data access by column key may have fewer supported operations or
 * worse performance than data access by row key.
 *
 * <p>The methods returning collections or maps always return views of the underlying table.
 * Updating the table can change the contents of those collections, and updating the collections
 * will change the table.
 *
 * <p>All methods that modify the table are optional, and the views returned by the table may or may
 * not be modifiable. When modification isn't supported, those methods will throw an {@link
 * UnsupportedOperationException}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#table"> {@code Table}</a>.
 *
 * @author Jared Levy
 * @param <R> the type of the table row keys
 * @param <C> the type of the table column keys
 * @param <V> the type of the mapped values
 * @since 7.0
 */
@GwtCompatible
public interface Table<R, C, V> {
  // TODO(jlevy): Consider adding methods similar to ConcurrentMap methods.

  // Accessors

  
Returns true if the table contains a mapping with the specified row and column keys. 
Params:
rowKey – key of row to search for
columnKey – key of column to search for/**
   * Returns {@code true} if the table contains a mapping with the specified row and column keys.
   *
   * @param rowKey key of row to search for
   * @param columnKey key of column to search for
   */
  boolean contains(
      @Nullable @CompatibleWith("R") Object rowKey,
      @Nullable @CompatibleWith("C") Object columnKey);

  
Returns true if the table contains a mapping with the specified row key. 
Params:
rowKey – key of row to search for/**
   * Returns {@code true} if the table contains a mapping with the specified row key.
   *
   * @param rowKey key of row to search for
   */
  boolean containsRow(@Nullable @CompatibleWith("R") Object rowKey);

  
Returns true if the table contains a mapping with the specified column. 
Params:
columnKey – key of column to search for/**
   * Returns {@code true} if the table contains a mapping with the specified column.
   *
   * @param columnKey key of column to search for
   */
  boolean containsColumn(@Nullable @CompatibleWith("C") Object columnKey);

  
Returns true if the table contains a mapping with the specified value. 
Params:
value – value to search for/**
   * Returns {@code true} if the table contains a mapping with the specified value.
   *
   * @param value value to search for
   */
  boolean containsValue(@Nullable @CompatibleWith("V") Object value);

  
Returns the value corresponding to the given row and column keys, or null if no such mapping exists. 
Params:
rowKey – key of row to search for
columnKey – key of column to search for/**
   * Returns the value corresponding to the given row and column keys, or {@code null} if no such
   * mapping exists.
   *
   * @param rowKey key of row to search for
   * @param columnKey key of column to search for
   */
  V get(
      @Nullable @CompatibleWith("R") Object rowKey,
      @Nullable @CompatibleWith("C") Object columnKey);

  
Returns true if the table contains no mappings. /** Returns {@code true} if the table contains no mappings. */
  boolean isEmpty();

  
Returns the number of row key / column key / value mappings in the table. /** Returns the number of row key / column key / value mappings in the table. */
  int size();

  
Compares the specified object with this table for equality. Two tables are equal when their cell views, as returned by cellSet, are equal. /**
   * Compares the specified object with this table for equality. Two tables are equal when their
   * cell views, as returned by {@link #cellSet}, are equal.
   */
  @Override
  boolean equals(@Nullable Object obj);

  
Returns the hash code for this table. The hash code of a table is defined as the hash code of its cell view, as returned by cellSet. /**
   * Returns the hash code for this table. The hash code of a table is defined as the hash code of
   * its cell view, as returned by {@link #cellSet}.
   */
  @Override
  int hashCode();

  // Mutators

  
Removes all mappings from the table. /** Removes all mappings from the table. */
  void clear();

  
Associates the specified value with the specified keys. If the table already contained a
mapping for those keys, the old value is replaced with the specified value.
Params:
rowKey – row key that the value should be associated with
columnKey – column key that the value should be associated with
value – value to be associated with the specified keys
Returns:
the value previously associated with the keys, or null if no mapping existed for the keys/**
   * Associates the specified value with the specified keys. If the table already contained a
   * mapping for those keys, the old value is replaced with the specified value.
   *
   * @param rowKey row key that the value should be associated with
   * @param columnKey column key that the value should be associated with
   * @param value value to be associated with the specified keys
   * @return the value previously associated with the keys, or {@code null} if no mapping existed
   *     for the keys
   */
  @CanIgnoreReturnValue
  @Nullable
  V put(R rowKey, C columnKey, V value);

  
Copies all mappings from the specified table to this table. The effect is equivalent to calling put with each row key / column key / value mapping in table. 
Params:
table – the table to add to this table/**
   * Copies all mappings from the specified table to this table. The effect is equivalent to calling
   * {@link #put} with each row key / column key / value mapping in {@code table}.
   *
   * @param table the table to add to this table
   */
  void putAll(Table<? extends R, ? extends C, ? extends V> table);

  
Removes the mapping, if any, associated with the given keys.
Params:
rowKey – row key of mapping to be removed
columnKey – column key of mapping to be removed
Returns:
the value previously associated with the keys, or null if no such value existed/**
   * Removes the mapping, if any, associated with the given keys.
   *
   * @param rowKey row key of mapping to be removed
   * @param columnKey column key of mapping to be removed
   * @return the value previously associated with the keys, or {@code null} if no such value existed
   */
  @CanIgnoreReturnValue
  @Nullable
  V remove(
      @Nullable @CompatibleWith("R") Object rowKey,
      @Nullable @CompatibleWith("C") Object columnKey);

  // Views

  
Returns a view of all mappings that have the given row key. For each row key / column key /
value mapping in the table with that row key, the returned map associates the column key with
the value. If no mappings in the table have the provided row key, an empty map is returned.
Changes to the returned map will update the underlying table, and vice versa.
Params:
rowKey – key of row to search for in the table
Returns:
the corresponding map from column keys to values/**
   * Returns a view of all mappings that have the given row key. For each row key / column key /
   * value mapping in the table with that row key, the returned map associates the column key with
   * the value. If no mappings in the table have the provided row key, an empty map is returned.
   *
   * <p>Changes to the returned map will update the underlying table, and vice versa.
   *
   * @param rowKey key of row to search for in the table
   * @return the corresponding map from column keys to values
   */
  Map<C, V> row(R rowKey);

  
Returns a view of all mappings that have the given column key. For each row key / column key /
value mapping in the table with that column key, the returned map associates the row key with
the value. If no mappings in the table have the provided column key, an empty map is returned.
Changes to the returned map will update the underlying table, and vice versa.
Params:
columnKey – key of column to search for in the table
Returns:
the corresponding map from row keys to values/**
   * Returns a view of all mappings that have the given column key. For each row key / column key /
   * value mapping in the table with that column key, the returned map associates the row key with
   * the value. If no mappings in the table have the provided column key, an empty map is returned.
   *
   * <p>Changes to the returned map will update the underlying table, and vice versa.
   *
   * @param columnKey key of column to search for in the table
   * @return the corresponding map from row keys to values
   */
  Map<R, V> column(C columnKey);

  
Returns a set of all row key / column key / value triplets. Changes to the returned set will update the underlying table, and vice versa. The cell set does not support the add or addAll methods. 
Returns:
set of table cells consisting of row key / column key / value triplets/**
   * Returns a set of all row key / column key / value triplets. Changes to the returned set will
   * update the underlying table, and vice versa. The cell set does not support the {@code add} or
   * {@code addAll} methods.
   *
   * @return set of table cells consisting of row key / column key / value triplets
   */
  Set<Cell<R, C, V>> cellSet();

  
Returns a set of row keys that have one or more values in the table. Changes to the set will
update the underlying table, and vice versa.
Returns:
set of row keys/**
   * Returns a set of row keys that have one or more values in the table. Changes to the set will
   * update the underlying table, and vice versa.
   *
   * @return set of row keys
   */
  Set<R> rowKeySet();

  
Returns a set of column keys that have one or more values in the table. Changes to the set will
update the underlying table, and vice versa.
Returns:
set of column keys/**
   * Returns a set of column keys that have one or more values in the table. Changes to the set will
   * update the underlying table, and vice versa.
   *
   * @return set of column keys
   */
  Set<C> columnKeySet();

  
Returns a collection of all values, which may contain duplicates. Changes to the returned
collection will update the underlying table, and vice versa.
Returns:
collection of values/**
   * Returns a collection of all values, which may contain duplicates. Changes to the returned
   * collection will update the underlying table, and vice versa.
   *
   * @return collection of values
   */
  Collection<V> values();

  
Returns a view that associates each row key with the corresponding map from column keys to values. Changes to the returned map will update this table. The returned map does not support put() or putAll(), or setValue() on its entries. 
In contrast, the maps returned by rowMap().get() have the same behavior as those returned by row. Those maps may support setValue(), put(), and 
putAll(). 
Returns:
a map view from each row key to a secondary map from column keys to values/**
   * Returns a view that associates each row key with the corresponding map from column keys to
   * values. Changes to the returned map will update this table. The returned map does not support
   * {@code put()} or {@code putAll()}, or {@code setValue()} on its entries.
   *
   * <p>In contrast, the maps returned by {@code rowMap().get()} have the same behavior as those
   * returned by {@link #row}. Those maps may support {@code setValue()}, {@code put()}, and {@code
   * putAll()}.
   *
   * @return a map view from each row key to a secondary map from column keys to values
   */
  Map<R, Map<C, V>> rowMap();

  
Returns a view that associates each column key with the corresponding map from row keys to values. Changes to the returned map will update this table. The returned map does not support put() or putAll(), or setValue() on its entries. 
In contrast, the maps returned by columnMap().get() have the same behavior as those returned by column. Those maps may support setValue(), put(), and putAll(). 
Returns:
a map view from each column key to a secondary map from row keys to values/**
   * Returns a view that associates each column key with the corresponding map from row keys to
   * values. Changes to the returned map will update this table. The returned map does not support
   * {@code put()} or {@code putAll()}, or {@code setValue()} on its entries.
   *
   * <p>In contrast, the maps returned by {@code columnMap().get()} have the same behavior as those
   * returned by {@link #column}. Those maps may support {@code setValue()}, {@code put()}, and
   * {@code putAll()}.
   *
   * @return a map view from each column key to a secondary map from row keys to values
   */
  Map<C, Map<R, V>> columnMap();

  
Row key / column key / value triplet corresponding to a mapping in a table.
Since:
7.0/**
   * Row key / column key / value triplet corresponding to a mapping in a table.
   *
   * @since 7.0
   */
  interface Cell<R, C, V> {
    
Returns the row key of this cell. /** Returns the row key of this cell. */
    @Nullable
    R getRowKey();

    
Returns the column key of this cell. /** Returns the column key of this cell. */
    @Nullable
    C getColumnKey();

    
Returns the value of this cell. /** Returns the value of this cell. */
    @Nullable
    V getValue();

    
Compares the specified object with this cell for equality. Two cells are equal when they have
equal row keys, column keys, and values.
/**
     * Compares the specified object with this cell for equality. Two cells are equal when they have
     * equal row keys, column keys, and values.
     */
    @Override
    boolean equals(@Nullable Object obj);

    
Returns the hash code of this cell.
The hash code of a table cell is equal to Object.hashCode(e.getRowKey(),
e.getColumnKey(), e.getValue()). /**
     * Returns the hash code of this cell.
     *
     * <p>The hash code of a table cell is equal to {@link Objects#hashCode}{@code (e.getRowKey(),
     * e.getColumnKey(), e.getValue())}.
     */
    @Override
    int hashCode();
  }
}